Field sprayers are used in agriculture for distributing sprayed agents on a field for fertilizing the field or for combating undesired organisms present there, such as weeds, fungi or insects. They are available as self-propelled or towed designs, or attached to or seated on a carrier vehicle. In order to achieve a sufficient working width of several tens of meters, sprayers are equipped with booms that support spray nozzles and that can be adjusted between a folded transport position for traveling on roads and an extended working position for field operation. The booms are usually designed to be relatively rigid in the vertical direction in order to maintain a constant distance between the ground and the spray nozzles and thus guarantee maintenance of the desired discharge rates, while they are designed to be less stiff in the forward direction for reasons of weight and cost. This has the disadvantageous result, however, that the boom can undergo oscillating movements in the forward direction, for example, when the field sprayer or a vehicle carrying it is decelerated or accelerated or travels on a curve. The amplitude of such oscillating movements can be on the order of 1 m or more, which has the undesired consequence that the desired discharge rates are not maintained in certain places.
A number of measures have been proposed for detecting and combating such oscillating movements by means of an electronic controller. For instance, DE 100 54 285 A1 proposes to detect the movements of the boom in the forward direction and cancel them by actuators (arranged to the left and the right of the longitudinal axis) operating in the opposite direction, which act on the boom on both halves of the boom and are articulated at the other end to the frame of the field sprayer. For active oscillation canceling, DE 10 2015 113 721 A1 proposes to move the boom as a whole in the forward direction relative to the frame of the field sprayer in order to reduce the effects of linear decelerations or accelerations of the field sprayer on the boom, whereas it is proposed in DE 10 2015 204 992 B3 to cancel the oscillation of the boom by means of air-ejecting nozzles that are mounted on the boom.
DE 10 2008 007 312 A1 proposes to attach an oscillation damper composed of a mass and a spring to the outer end of each boom half. The mass is not actively driven and is intended to automatically cancel out the oscillating movements of the boom.
EP 2 526 755 A1, EP 2 589 289 A2, EP 2 835 050 A1 and EP 2 829 177 A1 propose to mount damping elements inside the boom, the damping properties of which can be modified based on the type of movement of the field sprayer.
EP 3 132 682 A1, which is considered to define the class of apparatus in question, proposes to detect future movements of the field sprayer anticipatorily and, for example, to reduce the propulsion speed of the field sprayer as gently as possibly when traveling on curves or during linear accelerations or decelerations in order to reduce undesired oscillations. With an actively adjustable boom, a pre-acceleration of the boom can be carried out prior to cornering so that the acceleration of the boom about the vertical axis during the actual cornering is reduced.
DE 10 2014 203 005 B3 proposes to apply, upon an adjustment command, a first signal to an actuator to adjust a field sprayer boom that is adjustable in height or is rotatable about an axis running in the forward direction, and then to apply a second signal which has the effect that the oscillation in the boom that was induced by the first signal is canceled out. This procedure cannot be transferred to the problems in the art, however, because the undesired oscillation of the boom is not initiated by adjustment commands to an actuator moving the boom but rather by the acceleration of the field sprayer.
The known measures for oscillation damping thus comprise active elements which (directly or via the field sprayer) act mechanically on the boom (e.g., DE 100 54 285 A1, DE 10 2015 113 721 A1, DE 10 2015 204 992 B3 and EP 3 132 682 A1), passive oscillation dampers (e.g., DE 10 2008 007 312 A1, EP 2 526 755 A1, EP 2 589 289 A2, EP 2 835 050 A1 and EP 2 829 177 A1) and a limitation of the linear acceleration of the field sprayer (e.g., EP 3 132 682 A1) or the boom (e.g., DE 10 2015 113 721 A1). The active and passive elements for oscillation damping require a relatively high expense, whereas the limitation of the linear acceleration of the field sprayer or the boom will scarcely be sufficient to effectively cancel out the oscillations of the boom.